This invention relates to a heating and cooling lunch box in which the cooked contents can be thermally insulated at suitable temperature of taste in response to the type of cooking for a long period of time.
When a lunch box is generally heat insulated, a heat insulating vessel called "a lunch jar" is used. Since the insulating vessel has a body of vacuum bottle structure, the vessel has drawbacks such as being very expensive and large shape to be readily collapsible and inconvenient to carry.
In order to eliminate such drawbacks, a lunch box has been known, as disclosed in Japanese Utility Publication No. 18985/1982, in which an upper hollow heat radiator containing high temperature liquid therein and a lower heat radiator are provided to fill lunch in a space formed of both the radiators and a heat insulator is coated on both the radiators.
However, an idea of insulating a lunch box for a long time in both heating and cooking states of opposite properties has not been known. Dishes and hence particularly Japanese dishes have suitable temperatures of taste in response to the types, but the conventional lunch box is heat insulated entirely at the same temperature so as to be eaten at the same temperature. Thus, the content of the lunch box is limited or delicate taste responsive to the types of lunch is obviated at the time of eating the lunch.
When a large quantity of rice boiled in mass production in a production line is filled into lunch boxes and sold, the safety and sanitation of the lunch boxes must be most taken into consideration. However, since there is an anxiety of breeding bacteria in the conventional lunch boxes of simple heat insulation to be used for this purpose, the contents of the lunch boxes are limited from this point of view, and even if the contents are thus selected, there is still a danger of food poisoning.